Recovering hydrocarbons from subterranean zones relies on drilling wellbores.
Wellbores are made using surface-located drilling equipment which drives a drill string that eventually extends from the surface equipment to the formation or subterranean zone of interest. The drill string can extend thousands of feet or meters below the surface. The terminal end of the drill string includes a drill bit for drilling (or extending) the wellbore. Drilling fluid usually in the form of a drilling “mud” is typically pumped through the drill string. The drilling fluid cools and lubricates the drill bit also carries cuttings back to the surface. Drilling fluid may also be used to help control bottom hole pressure to inhibit hydrocarbon influx from the formation into the wellbore and potential blow out at surface.
Bottom hole assembly (BHA) is the name given to the equipment at the terminal end of a drill string. In addition to a drill bit a BHA may comprise elements such as: apparatus for steering the direction of the drilling (e.g. a steerable downhole mud motor or rotary steerable system); one or more downhole probes, stabilizers; heavy weight drill collars, pulsers and the like. The BHA is typically advanced into the wellbore by a string of metallic tubulars (drill pipe).
A downhole probe may comprise any active mechanical, electronic, and/or electromechanical system that operates downhole. A probe may provide any of a wide range of functions including, without limitation, data acquisition, measuring properties of the surrounding geological formations (e.g. well logging), measuring downhole conditions as drilling progresses, controlling downhole equipment, monitoring status of downhole equipment, measuring properties of downhole fluids and the like. A probe may comprise one or more systems for: telemetry of data to the surface; collecting data by way of sensors (e.g. sensors for use in well logging) that may include one or more of vibration sensors, magnetometers, inclinometers, accelerometers, nuclear particle detectors, electromagnetic detectors, acoustic detectors, and others; acquiring images; measuring fluid flow; determining directions; emitting signals, particles or fields for detection by other devices; interfacing to other downhole equipment; sampling downhole fluids, etc. Some downhole probes are highly specialized and expensive.
Downhole conditions can be harsh. Exposure to these harsh conditions, which can include high temperatures, vibrations (including axial, lateral, and torsional vibrations), turbulence and pulsations in the flow of drilling fluid past the probe, shocks, and immersion in various drilling fluids at high pressures can shorten the lifespan of downhole probes and increase the probability that a downhole probe will fail in use. Supporting and protecting downhole probes is important as a downhole probe may be subjected to high pressures (20,000 p.s.i. or more in some cases), along with severe shocks and vibrations. Furthermore, replacing a downhole probe that fails while drilling can involve very great expense.
There are references that describe various centralizers that may be useful for supporting a downhole electronics package centrally in a bore within a drill string. The following is a list of some such references: US2007/0235224; US2005/0217898; U.S. Pat. No. 6,429,653; U.S. Pat. No. 3,323,327; U.S. Pat. No. 4,571,215; U.S. Pat. No. 4,684,946; U.S. Pat. No. 4,938,299; U.S. Pat. No. 5,236,048; U.S. Pat. No. 5,247,990; U.S. Pat. No. 5,474,132; U.S. Pat. No. 5,520,246; U.S. Pat. No. 6,429,653; U.S. Pat. No. 6,446,736; U.S. Pat. No. 6,750,783; U.S. Pat. No. 7,151,466; U.S. Pat. No. 7,243,028; US2009/0023502; WO2006/083764; WO2008/116077; WO2012/045698; and WO2012/082748.
CA2735619 discloses snubber shock assemblies for measuring while drilling components that have natural frequencies that are less than a vibration frequency of an agitator.
U.S. Pat. No. 5,520,246 issued May 28, 1996 discloses apparatus for protecting instrumentation placed within a drill string. The apparatus includes multiple elastomeric pads spaced about a longitudinal axis and protruding in directions radially to the axis. The pads are secured by fasteners.
US 2005/0217898 published Oct. 6, 2005 describes a drill collar for dampening downhole vibration in the tool-housing region of a drill string. The collar has a hollow cylindrical sleeve having a longitudinal axis and an inner surface facing the longitudinal axis. Multiple elongate ribs are mounted to the inner surface and extend parallel to the longitudinal axis.
There remains a need for better ways to provide downhole probes at downhole locations in a way that provides enhanced resistance to damage from mechanical shocks and vibrations and other downhole conditions.